Easy-Downloader V1.1 with SDCC using AT89C2051

I am very happy to use sdcc for writing firmware of my project. The compiled code is very compact and nice. After I succeeded writing a new firmware of xtimer and Easy-downloader V1.1 with sdcc. I cannot stop preparing a new page that gives the idea how to use sdcc and of course it’s time to renovate my old project with orcad. For now I can design the hardware, draw a schematic, write the firmware and layout the pcb. So I think why shouldn’t begin with Easy-Downloader. Since the programmer board will enable learning and developing the small project with a cheap 20-pin MCU easily.

Hardware

The hardware has a bit change at rs232 level converter. Now the circuit uses a popular rs232 level converter, MAX232. Also I cut the bridge diode at the DC input, now I use only one diode to prevent wrong polarity of a given DC adapter.

Layout

The pcb layout was made with orcad Layout Plus. The gerber file is available at download section below. Here I like to show how nice it is. The top and bottom layers are shown in Figure 2 and Figure 3. Figure 4 shows the component placement layout.

Bill Of Materials

The component list is shown in Figure 5. U1 the master chip must be programmed with writer1.hex before the programmer board can run properly. Q2 and Q3 are TO92 plastic package! With a CAN package, pin positions may differ on the layout. You can use any small signal transistors to replace them. VB1 is male type! All resistors can be 1/4W or 1/8W 5%.